A wireless sensor network, which is composed of numerous sensor nodes distributed within a specific region, is a current research hotspot. The sensor nodes are capable of sensing circumstance, monitoring a specific event and performing wireless communication. After collecting data, the sensor node sends the data in a single-hop or multi-hop manner to a data sink where the data is stored for local use or uploaded for other network (such as the Internet) use. Ever since it was proposed at an end of last century, the wireless sensor network is developed rapidly and widely applied in fields of military affairs, transportation, environmental monitoring, etc.
However, the wireless sensor network also faces plenty of practical problems. One of severest challenges is that energy of sensor nodes is extremely restricted, which is mainly caused by following factors. Firstly, in most cases, sensor nodes rely on batteries, which cannot provide enough energy, as power supplies. Secondly, sensors are usually deployed in a region that is quite hard for humans to reach, which leads to difficulties in battery changing. Thirdly, as there are a lot of nodes in the wireless sensor network, a battery changing requires a large amount of manpower.
In recent years, an energy restriction challenge of the wireless sensor network changes. As application scenarios of the wireless sensor network change gradually from the specialized fields like military affairs and scientific research to people's daily life, such as healthcare, smart home, movement identification and the like. Moreover, the deployment of the sensor nodes gets closer and closer to people's living and working place, where various wireless devices coexist. Thus, how to save energy for the sensor nodes in these new application scenarios is of great significance.